This project will explore the hypothesis that chronic administration of cocaine, heroin or morphine, results in changes in the opioidergic, dopaminergic, and glutarnatergic systems in mesocorticolimbic and nigrostriatal regions of the brain that persist for long periods following drug withdrawal. These regions will be systematically examined for persistent changes in receptor binding and gene expression during chronic administration and following withdrawal from heroin or morphine or cocaine. We also selected the amygdala for a detailed ultrastructural analysis, since neurons in this region are involved in opiate and cocaine withdrawal, and also potently influence the stress responsive axis. In the amygdala, neither the relevant mu- and kappa-opioid receptors nor the dopamine D1 and D2 receptors have been examined by high-resolution methods capable of distinguishing the critical pre- (axonal) or post- (dendritic) synaptic plasmalemmal sites for receptor activation. Also, there is presently no information on potentially important long-term changes in the plasmalernmal expression of opiate related glutarnatergic (NMDA or AMPA) or peptide (substance P, NK1) systems in amygdaloid subnuclei following chronic morphine administration. We will specifically test the hypotheses that 1) opioid and dopamine receptors are targeted to functional sites on plasma membranes of region-specific amygdaloid neurons distinguished by their transmitters, projections, and substance P or subtype-selective glutamate receptor expression in rat, 2) chronic morphine administration produces long-lasting changes in the plasmalernmal availability of subtype-specific glutamate, dopamine, and peptide receptors within the amygdala of the rat, 3) chronic heroin or morphine administration or withdrawal produces regionally selective changes in expression of opioid and opioid system-related genes, and 4) chronic "binge" cocaine administration and withdrawal produce regionally selective changes in binding to receptors and transporters, or the expression of opioid and opioid system-related genes. We will use sensitive and complementary methods (light and electron microscopic immunocytochemistry, quantitative autoradiography, RNase protection, real-time optical RT-PCR, and microarray analyses) to directly address these fundamental unanswered questions regarding the normal distribution and drug-induced changes in receptor targeting, binding, and expression in animal models of human addiction.